A brake pedal may be depressed at an extremely high speed at times such as panic braking compared to the speed at which the brake pedal is operated during normal braking. In such cases, rear wheel locking precedent to front wheel locking can occur when the braking force distribution to the rear wheel side is increased while performing a front-rear braking force distribution control. Such rear wheel locking precedent to front wheel locking is undesirable because it destabilizes the vehicle condition.
Hence, Japanese Patent Application Publication No. JP-A-HEI6-336157 proposes starting a hydraulic control (pressure control) for the rear wheels earlier in the execution of the front-rear braking force distribution control so that rear wheel locking precedent to front wheel locking does not occur even at times such as panic braking.
However, starting the rear wheel hydraulic control earlier as mentioned above can also mean that the rear wheel hydraulic control starts before the rear wheel hydraulic pressure has been sufficiently increased. Consequently, it becomes impossible to ensure sufficient deceleration. In other words, it should be possible to obtain greater deceleration by increasing the hydraulic pressure to the rear wheels within a range that does not generate rear wheel locking precedent to front wheel locking. However, since the rear wheel hydraulic control is started regardless of the low hydraulic pressure, only deceleration corresponding to the low hydraulic pressure can be obtained. Although the rear wheel hydraulic pressure can be further increased especially in cases where the vehicle is loaded down with many occupants or much cargo, the maximum value of generable hydraulic pressure is determined too early, meaning that a large deceleration cannot be obtained.